A 1:1 combination of cannabidiol and Δ9-tetrahydrocannabinol inhibit toll-like receptor 7- and 8-mediated inflammation in human immune cells

Cannabinoid regulation of endosomal signalling via innate immune toll-like receptors (TLRs) is understudied. Endosomal cell signalling via TLR7 and TLR8 governs cellular responses to infection with viral and bacterial single-stranded RNA. TLR7/8 activation is associated with neuroinflammation, with inappropriate activation of TLR7/8 linked to the propagation of autoimmune disease. Following activation, TLR7 and TLR8 control the cellular production of cytokines, chemokines and type I interferons (IFNs). In this study we focused on two clinically relevant plant-derived (phyto) cannabinoids, cannabidiol (CBD) and Δ⁹-tetrahydrocannabinol (THC), given that cannabinoid-based therapeutics containing these compounds are currently available in the form of sativex® (nabiximols) and epidiolex®. The study aim was to determine the anti-inflammatory effects of CBD and THC, when delivered in isolation and in a sativex-like combination (1:1), on TLR7/8-induced inflammation in immune cells. We employed the use of CL075 (3M-002), a thiazoloquinolone derivative that acts as an agonist of both TLR7 and TLR8. Using THP-1-derived macrophages and primary peripheral blood mononuclear cells (PBMCs) from healthy control subjects, we demonstrate that TLR7/8 activation promoted the time- and concentration-dependent production of the chemokine CXCL10, cytokine TNFα and type I IFNs in both macrophages and PBMCs. TLR7/8 activation promoted nuclear factor (NF)-κB activation, p38 MAPK phosphorylation and the transcription of interferon regulator factor 7 (IRF7). We assessed the anti-inflammatory effects of CBD and THC, when delivered alone and in a 1:1 combination, on CL075-stimulated inflammatory mediator production in macrophages/PBMCs. Data presented herein indicate that CBD and THC, particularly when delivered in a 1:1 combination, can act as TLR7/8 immunomodulatory drugs to dampen inflammation in macrophages and PBMCs. This study provides evidence that phytocannabinoids target TLR7/8-induced viral signalling on endosomal compartments to control inflammation in immune cells.